1. Field of the Invention
This invention is related to sealed friction bearing rock bits.
More particularly, this invention is related to sealed friction bearing rock bits and a method to retain the cones on the journal bearings of the rock bit.
2. Description of the Prior Art
Typically, three roller cone rock bits are fabricated with the roller cones being locked to their respective journals by ball bearings introduced to a toroidal bearing track formed both in the journal bearing and the cone, the bearings being introduced through a ball hole drilled through the shirttail portion of each leg intersecting the toroidal track formed between the cone and the journal. As the bearings are introduced one by one, the track is eventually filled. A ball plug then is welded into the ball hole through the shirttail side of the rock bit leg.
The foregoing system of retaining roller cones on journals of rock bits inherently weakens the journals since a relatively large ball admitting hole is drilled through the shirttail portion of each leg of the rock bit.
U. S. Pat. No. 4,266,622, assigned to the same assignee as the present application, teaches a method to retain roller cones on journal bearings. This invention teaches the use of segmented cone retention ring members positioned in a deep slot formed in the bearing surface of the journal, the segments being subsequently E.B. welded, locking the roller cone on its journal. The segments, upon assembly, are inserted all the way into deepened slots in the journal so that they will clear the inside diameter of each of the cones during assembly of the cone on the journal. When the cone is properly aligned on the journal, the segments are E.B. welded within the cone bore by providing an access hole through the journal.
The present invention eliminates the need to metallurgically bond cone retention rings in rock bits. Moreover, the necessity to drill relatively large weld or ball access holes through each of the journals is eliminated by the instant invention.